Skip to main content

Screencast

start_screencast(**options) { |data, metadata, session_id| ... }​

Starts sending frames to record screencast to the given block.

  • options Hash

    • :format Symbol :jpeg | :png The format the image should be returned in.
    • :quality Integer The image quality. Note: 0-100 works for JPEG only.
    • :max_width Integer Maximum screencast frame width.
    • :max_height Integer Maximum screencast frame height.
    • :every_nth_frame Integer Send every n-th frame.

  • Block inputs:

    • data String Base64-encoded compressed image.
    • metadata Hash Screencast frame metadata.
      • "offsetTop" Integer Top offset in DIP.
      • "pageScaleFactor" Integer Page scale factor.
      • "deviceWidth" Integer Device screen width in DIP.
      • "deviceHeight" Integer Device screen height in DIP.
      • "scrollOffsetX" Integer Position of horizontal scroll in CSS pixels.
      • "scrollOffsetY" Integer Position of vertical scroll in CSS pixels.
      • "timestamp" Float (optional) Frame swap timestamp in seconds since Unix epoch.
    • session_id Integer Frame number.
require "base64"

page.go_to("https://apple.com/ipad")

page.start_screencast(format: :jpeg, quality: 75) do |data, metadata|
  timestamp = (metadata["timestamp"] * 1000).to_i
  File.binwrite("image_#{timestamp}.jpg", Base64.decode64(data))
end

sleep 10

page.stop_screencast

📝 NOTE​

Chrome only sends new frames while page content is changing. For example, if there is an animation or a video on the page, Chrome sends frames at the rate requested. On the other hand, if the page is nothing but a wall of static text, Chrome sends frames while the page renders. Once Chrome has finished rendering the page, it sends no more frames until something changes (e.g., navigating to another location).

stop_screencast​

Stops sending frames.